1112 General Notes. [ November, 
RATS NESTING IN TREES.—In the neighborhood of New Al- 
maden, Santa Clara county, Cal., I observed, during August of 
this year (1885), that in many of the small oaks there were masses 
of twigs, some of the masses as large as a bushel measure. On 
examination I found that each of the twigs showed evidence of 
having been gnawed off by some rodent. These nests proved to 
be inhabited by a species of rat about the size of the domestic rat, 
but finer looking, and with larger ears. They probably belong 
to the genus Neotoma of Say and Ord. The rat that builds a 
conical nest on the ground, of twigs and branches to the heighth 
of two or three feet, is probably of the same species as this living 
in the trees, as I found the nests of the two near together, and 
sometimes a nest wou'd be half on the ground and half in the tree. 
—H. W. Turner, U. S. Geol. Survey. 
PRELIMINARY NOTE ON THE ORIGIN OF Limps.—From my stud- ; 
ies on the limbs of vertebrates I get the following results : 
1. There exists no “ homodynamie” between the skeleton of 
the gills and the limbs (Thatcher, Mivart, Balfour, v. Rautenfeld, i 
Dohrn). | 
2. The original form of the paired fin is like that of the un- 
paired, and consists of parallel rays vertical to the axis of the 
body on a horizontal plane (Thatcher, Mivart, etc.). 
3. These rays unite proximally to form the dasiplerygmm, 
which turns out, forming the posterior border of the fin, the 
metapterygium (Balfour). 
4. The extremities of the higher vertebrates have originated 
directly from the fin by a rotation of the latter through 180° 10 
the direction of the hands of the clock. 
5. The extremities of the higher vertebrates have. originated 
by reduction of the propterygium and mesopterygium and the 
following rays of the metapterygium. 
6. A line drawn through humerus, radius, radiale, carpale 
me e,, digit, in the urodelous batrachians corresponds to 4 
line along the basipterygium, or the first ray of the metaptery” 
5 
um. : 
7. The oldest known extremities of the higher vertebrates arè 
seen in the Menopomidæ, in Salamandrella and Ranodon, among 
the batrachians (two central bones), in Plesiosaurus, Pliosaurus, 
_ Baptanodon (Sauranodon, rudiments of ulnar rays [“ olecranon ). 
fact of great interest is the presence of zwo central bones m É 
carpus of the Rhynchocephalia (Hatteria, Proterosaurus) never 
observed before. 
aa 8. The reduction of radial rays in the higher vertebrates is 2 
secondary condition produced by the adaptation to a terre a 
life —Dr. G. Baur, Yale College Mus., New Haven, Conn., Oct. 2, 
+ 
